The invention generally relates to color illumination sources. The invention particularly relates to organic light emitting illumination sources.
Previously disclosed color-tunable illumination devices, in particular white light illumination devices, require mixing of colors (for example, red, green, and blue light) to produce a desired color. Typically, the mixing of light with different colors is achieved with a diffuser film. A distance dependent on the pixel size and the arrangement of pixels has to be maintained between the diffuser and the illumination source in order to achieve a homogeneous appearance of mixed light. Typically, the smaller the pixels, the closer the diffuser distance and hence the overall lighting device is less bulky, e.g. in LCD displays. However, reducing the pixel size can significantly increase the cost of manufacturing due to extra pixels/area. Currently known techniques fall short of providing cost effective illumination sources with the required light intensity and color mixing.
It would therefore be highly desirable to provide a cost effective color illumination source, which can provide enhanced color mixing, without the drawbacks discussed above.